Same problem here. Reading the thread it's clear there's a bug in the Photos import feature.
I found that using the Windows import wizard works. You can access this by opening file explorer, clicking on "This PC", then right click on your connected device and select Import Pictures and Videos.
There's a guide here:
https://answers.microsoft.com/en-us/windows/forum/apps_windows_10-photos/complete-guide-to-importing-your-photos-in-windows/d8258fff-729e-45df-8afd-1f1195d7b6c5
I tried this but I got a lot of errors at first. Finally got somewhat of a download, but the majority of the pictures were in HEIC format which won't display in Windows 10. And, the .MOV movies are in HEVC format for which Microsoft wants you to buy an app
for $.99. Really?! That's insulting, to say the least.
So many people have had the Photos App problem for so long and Microsoft needs to FIX THIS PROBLEM!!! I have WASTED way too much time trying all the "fixes" and suggestions, and I and many other people still have not found a solution that works! Microsoft
needs to FIX THIS PROBLEM!!! Let me repeat!!!! -->
Microsoft needs to FIX THIS PROBLEM!!!
Microsoft needs to FIX THIS PROBLEM!!!
Microsoft needs to FIX THIS PROBLEM!!!
Microsoft needs to FIX THIS PROBLEM!!!